Patients with dementia may exhibit several types of delusions. Delusions have usually been described as simple and unsystematized paranoid beliefs, such as frequently accusing caregivers of stealing or being insincere or deceitful. Misidentifications—believing that another person is in the house or not recognizing one's own mirror image—also are common in patients with dementia. To further clarify the origin and clinical significance of delusions, the authors studied these behavioral disturbances in patients admitted to the 40-bed Alzheimer Unit at “Fatebenefratelli” Hospital in Brescia, Italy, and in community based patients with dementia.